Methods and devices for determining sensing device usability

Abstract

Methods and devices for determining device usability, e.g., for point of care assay devices. In one embodiment, the invention is to a method of determining device usability in a sensing device, including the steps of: providing a device comprising a first electrical pad; a second electrical pad; and a first polymer layer contacting at least a portion of the first and the second electrical pads and a second polymer layer contacting the first polymer layer and not the first and second electrical pads; applying a potential across the first and the second electrical pads; measuring an electrical property associated with the first and the second polymer layers; and determining whether the measured electrical property associated with the first and the second polymer layers has exceeded a threshold level associated with the device usability.

What is claimed is: 
     
       1. A method of applying a correction factor to a signal, comprising the steps of:
 providing a device comprising: a first electrical pad; a second electrical pad; a first polymer layer contacting the first electrical pad and the second electrical pad; and a second polymer layer contacting the first polymer layer and not the first electrical pad and the second electrical pad, wherein the first polymer layer comprises a polymer matrix and a plasticizer, and wherein the second polymer layer comprises a polymer matrix, a plasticizer, and an organic salt; 
 obtaining an initial current value associated with the first polymer layer and the second polymer layer that is measured when the device is manufactured, wherein a usability threshold level of the device is at least five times greater than the initial current value; 
 applying a potential across the first electrical pad and the second electrical pad; 
 measuring an electrical property associated with the first polymer layer and the second polymer layer based on the potential applied, wherein the measured electrical property predictably changes over time based on exposure of the device to environmental conditions, and wherein the electrical property comprises current, resistance, impedance, conductivity, or a combination thereof; 
 determining whether the electrical property exceeds the usability threshold level; 
 when the electrical property does not exceed the usability threshold level, determining the correction factor associated with the measured electrical property; and 
 applying the correction factor to the signal generated by a sensor to produce a corrected signal. 
 
     
     
       2. The method of  claim 1 , wherein the correction factor is selected from a group consisting of an amperometric correction value, a potentiometric correction value, a coulombic correction value and a conductivity correction value. 
     
     
       3. The method of  claim 1 , wherein the sensor is selected from a group consisting of a pH sensor, an oxygen sensor, a carbon dioxide sensor, a hematocrit sensor, a glucose sensor, a lactate sensor, a creatinine sensor, a sodium sensor, a potassium sensor, a chloride sensor, a calcium sensor, a BNP sensor, a troponin sensor, a CKMB sensor, a NGAL sensor, a TSH sensor, a D-dimer sensor, a PSA sensor, a PTH sensor, a cholesterol sensor, an ALT sensor, an AST sensor, a prothrombin sensor, an APTT sensor, an ACT sensor and a galectin sensor. 
     
     
       4. The method of  claim 1 , wherein the potential comprises a sigmoidal potential cycle, a fixed applied potential, a sequence of fixed applied potential steps, or a combination thereof. 
     
     
       5. The method of  claim 1 , wherein the potential comprises a potential cycle that is applied at a predetermined frequency in the range of about 1 Hz to about 100000 Hz. 
     
     
       6. The method of  claim 1 , further comprising inserting the device into an analyzer configured to determine whether the measured electrical property associated with the first polymer layer and the second polymer layer has exceeded the usability threshold level of the device. 
     
     
       7. A method of applying a correction factor to a signal, comprising the steps of:
 providing a device comprising: a first electrical pad; a second electrical pad; a first polymer layer contacting the first electrical pad and the second electrical pad; and a second polymer layer contacting the first polymer layer and not the first electrical pad and the second electrical pad, wherein the first polymer layer comprises a polymer matrix and a plasticizer, and wherein the second polymer layer comprises a polymer matrix, a plasticizer, and an organic salt; 
 obtaining an initial current value associated with the first polymer layer and the second polymer layer that is measured when the device is manufactured, wherein a usability threshold level of the device is at least five times less than the initial current value; 
 applying a potential across the first electrical pad and the second electrical pad; 
 measuring an electrical property associated with the first polymer layer and the second polymer layer based on the potential applied, wherein the measured electrical property predictably changes over time based on exposure of the device to environmental conditions, and wherein the electrical property comprises current, resistance, impedance, conductivity, or a combination thereof; 
 determining whether the electrical property exceeds the usability threshold level; 
 when the electrical property does not exceed the usability threshold level, determining the correction factor associated with the measured electrical property; and 
 applying the correction factor to the signal generated by a sensor to produce a corrected signal. 
 
     
     
       8. A method of applying a correction factor to a signal, comprising the steps of:
 providing a device comprising a first electrical pad; a second electrical pad; a first polymer layer contacting at least a portion of the first electrical pad; and a second polymer layer contacting at least a portion of the second electrical pad and at least a portion of the first polymer layer, wherein the first polymer layer comprises a polymer matrix and a plasticizer, and wherein the second polymer layer comprises a polymer matrix, a plasticizer, and an organic salt; 
 obtaining an initial current value associated with the first polymer layer and the second polymer layer that is measured when the device is manufactured, wherein a usability threshold level of the device is at least five times greater than the initial current value; 
 applying a potential across the first and the second electrical pads; 
 measuring an electrical property associated with the first and the second polymer layers based on the potential applied, wherein the measured electrical property predictably changes over time based on exposure of the device to environmental conditions, and wherein the electrical property comprises current, resistance, impedance, conductivity, or a combination thereof; 
 determining whether the electrical property exceeds the usability threshold level; 
 when the electrical property does not exceed the usability threshold level, determining the correction factor associated with the measured electrical property; and 
 applying the correction factor to the signal generated by a sensor to produce a corrected signal. 
 
     
     
       9. The method of  claim 8 , wherein the correction factor is selected from a group consisting of an amperometric correction value, a potentiometric correction value, a coulombic correction value and a conductivity correction value. 
     
     
       10. The method of  claim 8 , wherein the sensor is selected from a group consisting of a pH sensor, an oxygen sensor, a carbon dioxide sensor, a hematocrit sensor, a glucose sensor, a lactate sensor, a creatinine sensor, a sodium sensor, a potassium sensor, a chloride sensor, a calcium sensor, a BNP sensor, a troponin sensor, a CKMB sensor, a NGAL sensor, a TSH sensor, a D-dimer sensor, a PSA sensor, a PTH sensor, a cholesterol sensor, an ALT sensor, an AST sensor, a prothrombin sensor, an APTT sensor, an ACT sensor and a galectin sensor. 
     
     
       11. The method of  claim 8 , wherein the potential comprises a sigmoidal potential cycle, a fixed applied potential, a sequence of fixed applied potential steps, or a combination thereof. 
     
     
       12. The method of  claim 8 , wherein the potential comprises a potential cycle that is applied at a predetermined frequency in the range of about 1 Hz to about 100000 Hz. 
     
     
       13. The method of  claim 8 , further comprising inserting the device into an analyzer configured to determine whether the measured electrical property associated with the first and the second polymer layers has exceeded the usability threshold level of the device. 
     
     
       14. A method of applying a correction factor to a signal, comprising the steps of:
 providing a device comprising a first electrical pad; a second electrical pad; a first polymer layer contacting at least a portion of the first electrical pad; and a second polymer layer contacting at least a portion of the second electrical pad and at least a portion of the first polymer layer, wherein the first polymer layer comprises a polymer matrix and a plasticizer, and wherein the second polymer layer comprises a polymer matrix, a plasticizer, and an organic salt; 
 obtaining an initial current value associated with the first polymer layer and the second polymer layer that is measured when the device is manufactured, wherein a usability threshold level of the device is at least five times less than the initial current value; 
 applying a potential across the first electrical pad and the second electrical pad; 
 measuring an electrical property associated with the first polymer layer and the second polymer layer based on the potential applied, wherein the measured electrical property predictably changes over time based on exposure of the device to environmental conditions, and wherein the electrical property comprises current, resistance, impedance, conductivity, or a combination thereof; 
 determining whether the electrical property exceeds the usability threshold level; 
 when the electrical property does not exceed the usability threshold level, determining the correction factor associated with the measured electrical property; and 
 applying the correction factor to the signal generated by a sensor to produce a corrected signal.